AVDIIVKA, Ukraine — Strong shelling hit both government- and rebel-controlled areas of eastern Ukraine in a continued escalation of fighting. International monitors issued a sharp call for both sides to still their guns.
"Unacceptable! ... Sides have to stop fighting!" the monitoring mission of the Organization for Security and Cooperation In Europe said on its Facebook page.
Ukraine said three of its soldiers and an emergency worker died in the past day.
At least 33 people including civilians have been killed in fighting this week and several dozens injured.
Russian Foreign Ministry spokeswoman Maria Zakharova said Friday that several civilians were killed in the city of Donetsk, the main stronghold of Russian-backed separatist rebels, but did not give details.
The death toll in the war that began in April 2014 has exceeded 9,800, according to United Nations figures and a tally of recent fighting. Although a cease-fire and pullback of heavy weapons is called for in a two-year-old peace agreement, violations by both sides are frequent.
Fighting increased sharply on Sunday, with shelling from the rebel side centering on the town of Avdiivka, just north of Donetsk city. Each side blames the other for the upsurge.
U.S. Sen. John McCain, a strong critic of Russia, called on President Donald Trump to authorize sending lethal weapons to Ukrainian government forces.
The shelling in and around Avdiivka began on Sunday, the day Russian President Vladimir Putin and Trump spoke by telephone for the first time since Trump took office.
The timing "is an indication that Vladimir Putin is moving quickly to test you as commander in chief," McCain said in a letter to Trump.
Trump's repeated promises to improve relations with Russia have led to concerns in Ukraine that Washington would back off some of the sanctions imposed on Moscow for its involvement in eastern Ukraine and its annexation of the Crimean Peninsula.
Zakharova in turn lashed out at the Ukrainian government, saying the shelling of Donetsk "trampled on all moral norms."
A British photographer was wounded in the eye in shelling Thursday night, according to the Facebook page of Ukraine's anti-rebel military operation.
In the rebel stronghold of Donetsk, two civilians were killed late on Thursday in a neighborhood which was under intense fire in the recent days, the rebels' Donetsk News Agency said. Eight houses and two high schools were damaged in shelling Thursday night.
In Avdiivka, an industrial town whose pre-war population was about 35,000, residents were frightened and suffering through the loss of electricity and water supply amid a sharp cold snap.
"Of course, I'm really scared," said Tamara Tokmanova, who said her father had died in World War II. "My dad died, for such a bad life for me!"
OSCE monitors on Friday visited a water filtration plant near the front line which has been damaged in recent shelling. The plant is crucial for the clean water supply on both sides of the conflict. Alexander Hug, deputy head of the OSCE monitoring mission in Ukraine, warned that damage to the water plant in Yanysuvata, which has cut the supply to Avdiivka, can lead to a "potential humanitarian and ecological disaster."
Jim Heintz and Nataliya Vasilyeva in Moscow contributed to this story.